4J4  Official  Prunus  Virginiana.  {^^SuSf"1 
J  AN  INVESTIGATION  OF  THE  OFFICIAL*  PRUNUS 
VIRGINIANA,  TO  DISTINGUISH  IT  FROM 
BARKS  COLLECTED  AT  OTHER 
SEASONS.1 
By  Grace  E.  Cooi,by. 
A  contribution  to  the  work  of  Research  Committee  C,  of  the  Revision 
Committee  U.S. P. 
The  U.S.P.  prescribes  that  wild  cherry  bark  be  collected  in 
autumn,  when  it  yields  the  greatest  amount  of  hydrocyanic  acid. 
This  investigation  has  failed  to  furnish  any  distinctive  histological 
mark  of  the  bark  collected  in  autumn,  and  the  results  have  tended 
to  the  belief  that  the  suitable  test  is  a  chemical  one,  not  readily  to 
be  found  by  the  use  of  the  microscope. 
The  following  results  are  presented  with  tests  which  are  found 
accurate,  so  far  as  they  have  been  applied. 
The  researches  of  Fischer2  have  shown  us  the  phases  which 
starch  undergoes  in  the  bark  and  wood  of  most  trees  during  the 
year.  These  have  been  verified  with  regard  to  Prunus  serotina,  and 
give  us  an  easy  means  for  rejecting  all  barks  collected  in  summer 
and  winter,  for  they  contain  no  starch  at  all,  or  very  little.  During 
September  and  late  summer  the  starch  is  being  stored  up  in  the 
bark,  and  reaches  its  maximum  amount  in  October  and  the  first 
days  of  November,  just  after  leaf-fall.  At  this  time  all  the  cells  of 
the  medullary  rays,  and  the  bast  parenchyma,  as  well  as  the  chloro- 
phyll-bearing cells,  are  crowded  with  starch,  which  occurs  in  Prunus 
serotina,  in  small  round  grains.  This  gradually  disappears,  first 
from  the  parenchyma  of  the  bast,  and  last  from  the  medullary  rays. 
By  the  last  of  November  the  bark  is  nearly,  if  not  quite,  free  from 
starch,  and  remains  so  during  the  winter.  During  the  last  days  of 
February,  or  early  in  March,  a  process  of  starch  regeneration 
begins.  In  specimens  collected  March  21st  the  parenchyma  cells  of 
the  bast  contained  a  few  scattered  grains,  and  there  was  a  little  in 
those  cells  of  the  medullary  rays  which  lay  close  to  the  wood. 
Specimens  of  April  6th  showed  an  increase  in  all  the  cells  of  the 
bark,  and  April  21st,  the  maximum  was  nearly  reached,  for  the  bast 
parenchyma  and  medullary  rays,  as  well  as  the  green  cells,  contained 
xJour.  Pharmacology,  4.  167. 
2  Dr.  Alfred  Fischer,  PhysiologiederHolzgewach.se Jahrbiicher  fur  JViss.  Bot.y 
1891,  Sec.  73- 
